A battery is an electrochemical generator containing one or more galvanic cells in a finished package. Each individual cell is made up of an anode and a cathode made of dissimilar materials and separated by an electrolyte. In operation, the respective electrodes are connected via an external circuit which includes a device in which useful work is to be done, in the case of a discharging cell, or which is capable of doing work on the cell, for the case of a cell which is being recharged. The electrical circuit is completed by the electrolyte, which contains ionic species which transfer charge between the electrodes when the cell is discharging or charging.
Primary batteries are devices initially assembled with high energy chemical compounds, sold in their charged state, and PG,5 discarded without being recharged after the stored chemical energy has been withdrawn as electrical energy. Secondary batteries are rechargeable devices in which the chemical conditions of the undischarged battery can be restored by applying a current through the cells in the opposite direction from the current flow of the battery in its discharging mode.
The light atomic weight metals employed in light metal anode electrochemical cells are highly electrochemically reducing materials. Their use precludes the use of water or other weakly proton-donating solvents as well as numerous solvents which decompose or fail to form passivating films upon exposure to the anode. Nonaqueous matrices are therefore required in cells employing such light metal anodes. Such nonaqueous matrices may be either nonaqueous liquids or certain polymeric materials in which the conductive salts may be included. Typical solvents include tetrahydrofuran, 2-methyltetrahydrofuran, ethylene carbonate, propylene carbonate, dioxolane, 4-methyldioxolane, 1,2-dimethoxyethane, sulfolane, .gamma.-butyrolactone, methylformate, methyl acetate, diethylcarbonate, acetonitrile and sulfur dioxide. Commonly used polymeric solvents include numerous polyethers and ether-containing polymers.
The ionizable salts employed in nonaqueous electrolytes have generally utilized anions such as BF.sub.4.sup.-, PF.sub.6.sup.-, AsF.sub.6.sup.-, ClO.sub.4.sup.-, AlCl.sub.4.sup.-, SbF.sub.6.sup.-, CF.sub.3 SO.sub.3.sup.-, (CF.sub.3 SO.sub.2).sub.2 N.sup.-, and .sup.- B(A).sub.x (A').sub.y where A is alkyl, A' is aryl, and x+y=4. These materials suffer from one or more of the disadvantages of thermal instability (BF.sub.4.sup.-, PF.sub.6.sup.-, and AsF.sub.6.sup.-), potentially explosive character (ClO.sub.4.sup.-), being electrochemically non-passivating upon reduction (AlCl.sub.4.sup.-, SbF.sub.6.sup.-), affording electrolytes having marginally adequate conductivities for many applications (CF.sub.3 SO.sub.3.sup.-), and difficulty in preparation and purification (B(A).sub.x (A').sub.y.sup.-). These deficiencies of available electrolyte salts have retarded the development of light metal anode batteries having optimized capacities and reduced weights. Use of presently-available electrolyte salts has resulted in batteries having sub-optimal performance characteristics such as limited operating temperature ranges and limited discharge/charge rate performance.
U.S. Pat. No. 4,505,997 of Armand dicloses bis(perhalogenoacyl or perhalogenosulfonyl) imides of certain metals, for use in battery electrolytes. Armand's compounds have the general formula (C.sub.n X.sub.2n+1 Y).sub.2 N.sup.- M.sup.+ in which X is a halogen, n is an integer from 1-4, Y is a CO or SO.sub.2 group, and M is an alkali metal, preferably lithium or sodium, and possibly potassium. These materials appear to offer good thermal stability, but their conductivities in nonaqueous matrices are lower than desirable.
In a paper by Turowsky and Seppelt published in Inorg. Chem., 27, 2135-2137 (1988), the trisubstituted methane compound (CF.sub.3 SO.sub.2).sub.3 CH and four of its salts were disclosed in the context of an attempt to form a stable xenon-carbon bond. In the course of the investigation the K, Rb, Cs, and Ag salts of the tris(trifluoromethylsulfonyl) methane were prepared. Although the related anion (CF.sub.3 SO.sub.2).sub.2 N.sup.- had been reported to form a chemical bond to xenon, Turowsky and Seppelt were unsuccessful in achieving a carbon-xenon bond with their compound. The ability of (CF.sub.3 SO.sub.2)N.sup.- to form Xe--N bonds indicates the nitrogen is quite electrophilic, even though it is the formal site of negative charge, and that the electron density is actually quite delocalized through the anion. Negative charge delocalization is a property shared by the anions of highly conductive Li salts of organic anions. The failure of (CF.sub.3 SO.sub.2).sub.3 C.sup.- to bond to xenon suggests the central carbon retains greater negative charge density and would suggest that Li(CF.sub.3 SO.sub.2).sub.3 would exhibit low conductivities.
U.S. Pat. No. 4,049,861 of Nozari generically discloses highly fluorinated aliphatic sulfonic and sulfonylic compounds as catalysts useful in the preparation of abrasion resistant coatings. The compound (CF.sub.3 SO.sub.2).sub.3 CH was exemplified in a table, and metal salts of this and related compounds containing highly fluorinated alkyl groups are mentioned. This reference does not teach how to make any of the compounds within its generic disclosure, and does not suggest that such compounds have any other uses besides the catalytic utility disclosed.
A need exists for improved electrolyte salts for use in electrochemical cells which employ light metal anodes, for electrolytes containing such salts, and for improved batteries containing such electrolytes. Such improved electrolyte salts, electrolytes, and batteries are the subject of the present invention.